static <A> Scored<A> lambdaMapLike bestOfN(IF1<A, Double> scoreFunction, int n, IF0<A> produce) {
  new Best<A> best;
  
  repeat n {
    A a = produce!;
    double score = scoreFunction.get(a);
    best.put(a, score);
  }
  
  ret best.scored();
}